SPONSORED FEATURE DESIGN FOR MANUFACTURE WHY A KNOWLEDGE OF MANUFACTURING MATTERS To save time and money, if you don’t want to run into unwelcome problems when a
bespoke design gets to an outsourced production stage, do two important things, says Chris Arnold of manufacturing subcontractor ICEE Managed Services
F
irst, before getting immersed in design detail, talk to your selected contractor’s
design and manufacturing engineers and watch relevant production processes on the shopfloor. Second, besides the contractor providing a cost-saving 3D CAD model, where appropriate, consider investing in a physical working prototype. Both actions will help you see not only
new possibilities now, but also avoid troublesome issues later. That all adds up to achieving desired results in the shortest possible time, at least cost, with minimum risk and maximum benefits. Behind the above is a fundamental
question that has always dogged the design profession - how much do you need to know about manufacturing processes? Suppose you are designing a bespoke sheet metal structure. It could be for an architectural, automotive, consumer goods, medical engineering or other industry sector. Is it best to design what you regard as the ideal, without knowing how it will be made, then let production and value engineers decide how it will be manufactured? Or, to retain full control, do you investigate and specify the best way to make your design, based on advice from specialists? At ICEE we encounter both and arguably,
the best approach is probably the latter. It is more efficient and productive. It helps a great deal if the designer understands manufacturing processes, sees what causes difficulties and designs accordingly. It often leads to better innovation. Additionally, learned sources say 70-80 per cent of product costs are generated at the concept stage, which includes design for manufacture, so it pays to look very carefully at what can be done right-first-time in this critical area. So what are all the potential issues? On the
sheet metal side, whether it’s a simple panel or a complicated fabrication, here are some examples. Let’s assume the fundamentals have already been covered – a requirements specification from the customer. This can range from a ‘fag packet’ sketch to a full set of engineering drawings and bill of materials. If the end product we are making for a customer is a completely fitted-out assembly, ideally the specification should include reference to all regulatory standards and compliances.
16 MAY 2020 | DESIGN SOLUTIONS
DESIGN FOR MANUFACTURE Using advanced optimisation software and our combined experience, when we quote for a job we usually discover details where savings or improvements may be made on the design for manufacture side. With details that would be very costly or impossible to make, we suggest an alternative, enabling the designer to effect a timely and beneficial adjustment. Significant money may be saved and quality improved just with changes arising from this initial analysis and highly constructive consultation process. For example, with panels featuring several
bends, flanges, holes for attaching hinges, welded studs and other features, we take a CAD STEP file from the customer and flatten out the sheet metal design. This generally reveals several critical factors – what the true dimensions of the flat part must be to allow for important ‘K’ factor bending allowances; whether holes or apertures are too close to bends and risk distortion; whether the bend radii specified are correct for the sheet metal thickness; and economically, how many ‘nested’ parts may be cut from a sheet metal stock panel to minimise wasteful and costly scrap. Another example is an important feature or
characteristic most designers may not be aware of, but we deal with all the time – sheet metal has a ‘grain’ or directional bias. The raw material is produced in rolling mills, which gives rise to
this effect, but why does it matter? Because when being processed, a flange or bend formed with or against the grain will have more or less resistance to bending. This can affect the tightness of a bend, cause stressing and cracking, or result in over or under-bending. Either way, we check and adjust to ensure the bend ends up exactly as specified by the designer, without any issues.
AVOID HAZ RISKS Risk is key in the next example and in this case, knowing about processes is vital for safety. It concerns welding sheet metal panels together, such as when butted and welded edge to edge in one plane. If a panel is profile-cut by fibre laser (or another method that cuts metal by melting it) the intense heat generated forms oxides or heat-affected zones (HAZ) on cut metal surfaces – top, bottom and edge - along the length of cuts. If this oxide is not removed before welding
the butted panels together, the risk is it will contaminate a part or the whole weld. Entrapped oxide may weaken the weld’s strength. This will be especially important if panels are built into safety-critical products, such as passenger-carrying transport for use on land, sea or in the air. Over time, in areas affected by oxide inclusion, operational stresses may cause crack
An advanced waterjet cutting machine, used by ICEE to cut not only a variety of 2D profiles out of metal and plastic sheet, but also 3D parts out of thick materials
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